1. Field of the Invention
The present invention relates to a communication device and a communication method that enables recompression and transmission of JPEG data.
2. Description of the Related Art
Some conventional color facsimile devices adjust the JPEG compression ratio by selectively using quantization tables and are therefore provided with a variety of quantization tables. Japanese Patent Application Publication No. 2001-61068 discloses selecting a quantization table depending on the state of the used phone line in compressing a color image using JPEG and transmitting the resulting JPEG data to a remote facsimile device.
However, even a simple recompression of JPEG data involves a large number of quantization tables and requires that the entire compression procedure sequence be reversed to decompress the compressed image. Specifically, prior to recompression, the image data must be decompressed to restore the original image. Note that the decompressed data will differ slightly from original image data. Then, the most suitable quantization table has to be selected to perform JPEG recompression. Recompression performed according to this method is time-consuming and prevents efficient JPEG data transmission.